"WARNING SIGN" indicates a hazardous situation which, if not avoided, MAY result in death or personal injury.

Post warning signs in areas where equipment may be affected by stress cracking and metal fatigue. Metal fatigue, including hydrogen embrittlement or sulfide stress cracking, can result in a release of hydrogen sulfide gas. Possible hazards may occur by getting Injured due to equipment failure. Hydrogen sulfide reacts with metal ions to form metal sulfides, which may be considered the salts of hydrogen sulfide. Some ores are sulfides. Metal sulfides often have a dark color. Lead(II) acetate paper is used to detect hydrogen sulfide because it turns grey in the presence of the gas as lead(II) sulfide is produced. Reacting metal sulfides with strong acid liberates hydrogen sulfide. If gaseous hydrogen sulfide is put into contact with concentrated nitric acid, it explodes.